Problem of natural law in Aristotle

In reading Aristotle's ethical, political, and jurisprudential writings we often come upon the term physis, which we may translate as "by the order of nature." In ancient political theory this term physis was often contrasted with nomos or "that which is by convention." I will argue in this paper that Aristotle's use of the term physis in certain ethical, political, and legal texts does not imply a natural law doctrine as it is usually understood. For to so interpret the term physis would render much of his ethical, legal, and moral Philosophy; incoherent.